Process for the production of alpha,beta-unsaturated carboxylic acids

ABSTRACT

A PROCESS FOR THE PRODUCTION OF LONG CHAIN A,B UNSATURATED CARBOXYLIC ACIDS COMPRISES REACTING A B-HYDROXY NITRILE WITH AN AQUEOUS MINERAL ACID, AND THERMOLYZING THE RESULATNT PRODUCT.

United States Patent Olfice US. or. 260-413 11 Claims ABSTRACT OF DISCLOSURE A process for the production of long chain a,B-unsatu rated carboxylic acids comprises reacting a B-hydroxy nitrilewith an aqueous mineral acid, and thermolyzing the resultant product.

PRIOR ART The present invention relates to a process for the production of c p-unsaturated carboxylic acids.

*It is known that u,;8-unsaturated carboxylic acids can be obtained from low molecular weight range B-hydroxynitriles, for example, in a process for the manufacture of acrylic acid. However, a technically practical process for producing long chain higher mil-unsaturated carboxylic acids from corresponding hydroxynitriles has not previously been described. Even for working on a laboratory scale, synthesis reactions, such as the Perkin synthesis or the Knoevenagel reaction have been proposed, which are not operable for a technical production ofhigher u-B-uusaturated carboxylic acids.

OBJECTS OF THE INVENTION It is an object of the present invention .to provide a process for producing long chain a,B-unsaturated carboxylic acids by reacting a flehydroxynitrile with an aqueous mineral acid, and thermolyzing the resultant product.

It is another object of the present invention to provide a process for the production of long'chain c p-unsaturated carboxylic acids of the formula wherein R R and R, each represent a member selected from the group consisting of hydrogenand alkyl having 3 to 22 carbons, with the proviso that the total number of carbon atoms in R R and R is at least 3 andno more than 22 consisting essentially of the. steps of treating a fi-hydroxynitrile of the formula in which R R R}, have the above assignedmeanings 3,822,300 Patented July 2, 197.4

production of long chain a s-unsaturated carboxylic acids of the formula wherein R R and R each represent a member selected from the group consisting of hydrogen and alkyl having 3 to 22 carbons, with the proviso that the total number of carbon atoms in R R and R is at least 3 and no more than 22, consisting essentially of the steps of treating a fi-hydroxynitrile of the formula OH H in which R R K; have the above assigned meanings with an aqueous mineral acid at a temperature of from 50 to 250 C.; separating the aqeuous phase, thermolyzing the resultant product at a temperature of from 100 to 400 C.; and recovering the said 0a,)3-l1l153tl113t6d carboxylic acids.

The B-hydroxycarboxylic acid nitriles to be used as starting materials in the process of the present invention can be obtained in a particularly advantageous manner by reacting epoxides with prussic acid in the liquid phase in the presence of a catalyst e.g., a strong base and/or a compound forming cyanide ions.

Acid treatment of the fl-hydroxynitriles to be carried out in the first stage of the process of the present invention can be effected by means of conventional mineral acids such as hydrochloric acid, sulfuric acid, phosphoric acid, or even complex acids, With the acid concentration being dependent upon the particular acid used. Advantageously, the ratio between aqueous mineral acid and hydroxynitrile is chosen such that there are from 1 to 5 mols, preferably from 1 to 3 mols, of acid present for each mol of hydroxynitrile. In general, the aqueous mineral acid concentration ranges from 50% to 90%. The mols of mineral acid are calculated as anhydrous acid.

Preferablythe acid treatment is effected with sulfuric acid concentrations of from 50% to 80%, particularly from to being used.

The reaction temperature to be used during the acid treatment in the first stage is also dependent, to a certain extent, (a) upon the nature of the mineral acid to be used, (b) upon the acid concentration of the reaction mixture and (c) upon the hydroxynitrile used. Advantageously, in a preferred embodiment of the process which uses from 50% to sulfuric acid in a quantity ratio of from 1 to 5 mols of sulfuric acid per mol of hydroxynitrile, the reaction temperature in the first stage of the process is from 80 to 150 C.

The'duration of acid treatment is also variable, depend- .ing .(a) .upon the acid concentration, (b) upon the rewith an aqueous mineral acid at a, temperature of from 50 to 250 C.; separating the aqueous phase, the'rmolyzing the resultant product at ia temperature of from to 400 C., and recovering thesaid cap-unsaturated car boxylic acids.

Other and further objects of the present invention become apparent as the descriptionthereof proceeds.

. -DES ORIPTI.ION,OF THE INVENTION" action temperature and (c) upon the nature of the hydroxynitrile to be converted, and may be from 15 min utes to several hours. The course of the reaction may be observed by checking the hydroxynitrile content, with the optimum time conditions being established by taking into account the other reaction parameters.

'The reaction between a hydroxynitrile and a mineral acid can be effected in a simple manner by heating and stirring a mixture of hydroxynitrile and mineral acid in the above-mentioned quantity ratio to the desired reaction'temperature and continuing the heating until the I nitrile content in the reaction mixture has fallen below a detectable level.

70 The present invention isdirectedto a processfor the .The organic phase of the reaction mixture is subsequently separated, preferably while still hot, and can be directly used as such in the second stage of the process.

P articularly pure final products are obtained if the reac- I or in any case, a fl-sulfocarboxylic acid amide would be the expected result as taught in U.S. Pat. 2,425,694. In view of that U.S. patent there is a strong teaching and suggestion away from the process of the present invention, since this U.S. patent states that-in the case of ethylenecyanhydrine complete conversion of the nitrile group can be obtained only in an anhydrous medium, i.e. with anhydrous sulfuric acid, whereas the reaction is always incomplete when water is present in the reaction mixture. In contrast to this teaching, it has been found according to the present invention that rapid and complete conversion of the nitrile groups is possible when Working in the aqueous medium, and even a fully N-free product resultsas the end product of this reaction.

The thermolysis of the product of the first stage of the process is carried out in the second stage of the process. This thermolysis may be effected in a particularly advantageous manner by simultaneous distilling-01f under a vacuum the unsaturated carboxylic acids produced by the thermolysis. Alternatively, however, thermolysis may be carried out under normal pressure. This latter method is of advantage when higher molecular hydroxynitriles are used as starting materials in the process in accordance with the invention. In such cases the working-up of the products with thermolysis may be effected in a conventional manner, i.e. the raw products may be purified by re-crystallization, re-dissolving, extraction or treatment with adsorption agents. However, since the raw products obtained by thermolysis with simultaneous distilling-off 40 as well as those obtained by thermolysis under normal pressure already have a high degree of purity, further purification will not be required for manyintended uses.

In a preferred embodiment of the process of the present invention, the total number of carbon atoms in R R and R is at least 6 and no more than 16. In an especially preferred embodiment of the present invention, the p-hydroxynitrile reactant is selected'from the group consisting of B-hydroxytridecanoic, nitrile, fl-hy-p droxynonanoic nitrile, fl-hydroxyundecanoic nitrile, B-hydroxyheptadecanoic nitrile and B-hydroxynonadecanoic nitrile, and produces an wit-unsaturated carboxylic acid correspondingly selected from the group consisting of tridecenoic acid, nonenoic acid, undecenoic acid, heptadecenoic acid and nonadecenoic acid. r

The products produced by the process of the present I of theirsalts as soaps or as raw materials for producing fatty alcohols-,fatty amines; or fattynitriles," and as start- 2 kg. of sulfuric acid and 1 kg. B-hydroxytr i- 'decanoic nitrile (molar ratio 2.5 :1)'were stirred for 6 'hours and heated to 115 "to 120 C. The organic phase of the reaction mixture, in which nitrogen was no longer detectable, was separated at temperatures of from 60 to C. This organic phase ,was then heated to 210 to 240 C. in a distilling apparatus having a tempered cooler under an oil pump vacuum (0.2 to 0.05 torr). An

almost colorless liquid distilled 011 above 150 C. which solidified upon cool-ing. Virtually no residue remained in the distilling flask after heating for a sufficiently long period. The total quantity of distillate was 944 g., i.e. the'yield of tridecenoic acid was of theory. The

distillate had the following characteristics and analysis data which were in close conformity to the values calculated for tridecenoic acid.

Melting point C.) 35-36 Acid number: k

Found 249.9 Calculated 264.3 Saponification number: Found I 249 Calculated 264 Iodine value (by hydrogenation):

Found 118 Calculated 119 Molar weight:

Found 214 Calculated 212.3

Analysis data: l

C, found 73.1 C, calculated 73.5 -H, found ..L 11.8 H, calculated 11.4 0, found 15.1 *0, calculated 15.1

EXAMPLES 2 to 5 The hydroxy nitriles set forth below were converted into the corresponding mil-unsaturated carboxylic acids in a manner, analogous to that given in Example 1. The period of hydrolysis was. 6 hours in each case; the hydrolysis temperature was to ,120 C., and the mineral acid (sulfuric acid) concentration was 60%. The products which resulted upon hydrolysis were thermolyzed at the temperature given.

Example number l-cyanol-cyanol-eyanol-cyano- Z-hydroxy- 2-hydroxy- 2-hydroxy- 2-hydroxyoctane deeane hexadecane oetadecane Thermolysis temperature '('C.)" "220-240 210-230 220-250 210-250 Yield (percent of theory) V a t 77 '87. 90 5 93 13.1 (0.05-1 torr) (3.). 100-110 -135 I p -170 -184 M.P. C.) Liquid Liquid 50-68 61-62 Acid number 341(362; 294 (302) 101 (210) 179 (189) Saponifieation number 353 (362 292 (302) 196 (210) 186 (188) Ester number '1 0 5 Molar weilghthunu (156) 186 271 (268) 301 (296) Iodineva ue by hydr 153 (163) 129 (137) I 85 (95) 88 (86) Percent 68.7 (69.4) 71.1 (71.4) 74.8 76.0) 76.6 (77.1) Percent H---" I 10.4 (10.3) 10.9 (10.-9) 12.7 (11.9) 12.7 (12.2) PercentO 21.5 (20.4) 17.5 (17.3) 11.9 (11.9) 11.2 (10.8) Ester number of the primary product 189 r 135 121 I Osmometric in acetone.

N out-The numbers in parentheses are the calculated values.

EXAMPLE 6 EXAMPLE 7 0.529 kg. (2.5 mol) of 1-cyano-2-hydroxydodecane and 0.715 kg. of 85% phosphoric acid were stirred together for 6 hours while heated to 120 C. Double the volume of water was subsequently added to the reaction mixture and the mixture was heated to boiling. After the organic phase had been separated and dried, this phase was thermolyzed under oil pump vacuum (0.05 to 0.1 torr) at 170 to 230 C. (sump temperature) with simultaneous distillation of the trans-Z-trideoenoic acid produced. The yield amounted to 80% of theory.

EXAMPLE 8 Example 1 was repeated but the molar ratio between nitrile and sulfuric acid in the first stage of the process was 1:1.5; the reaction temperature was 134 to 136 C. and hydrolysis lasted for 2 hours. The end product, tridecenoic acid, was obtained in a 87% yield.

EXAMPLE 9 The same amounts of 0.5 kg. of 1-cyano-2-hydroxyoctadecane were hydrolyzed for 5 to 6 hours with sulfuric acid of dilferent concentrations (with constant molar ratio of nitrilezsulfuric acid of 1:25) at differing reaction temperatures, and the primary products were thermolyzed at the temperatures given below. The method was otherwise analogous to the method given in Example 1. The yields of nonadecenoic acid were as follows:

Hydrolysis Thermolysis temperature, temperature, Yield,

H SOreoncentratlon, percent 0. 0. percent Although the present invention has been disclosed in connection with a few preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the new invention. All of these variations and modifications are considered to be within the true spirit and scope of the present invention as disclosed in the foregoing description and defined by the appended claims.

We claim:

1. A process for the production of long chain 1!,fl-UI1 saturated carboxylic acids of the formula R1-C=CCOOH wherein R R and R each represent a member selected from the group consisting of hydrogen and alkyl having 3 to 22 carbons, with the proviso that the total number of carbon atoms in R R and R is at least 3 and no more than 22, consisting essentially of the steps of treating a p-hydroxynitrile of the formula in which R R R have the above assigned meanings with an aqueous mineral acid at a temperature of from 50 to 250 C.; separating the aqueous phase; thermolyzing the resultant product at a temperature of from 100 to 400 C.; and recovering the said u,13-unsaturated carboxylic acids. 7

2. The process as claimed in claim 1 in which the treatment with the mineral acid is carried out at a temperature of from to 150 C.

3. The process as claimed in claim 1 in which there are from 1 to 5 mols of mineral acid, calculated as anhydrous acid, present per mol of hydroxynitrile.

4. The process as claimed in claim 3 in which there are from 1 to 3 mols of mineral acid calculated as anhydrous acid, present per mol of hydroxynitrile.

5. The process as claimed in claim 1 in which the mineral acid is sulfuric acid.

6. The process as claimed in claim 5 in which the sulfuric acid has a concentration of from 50% to 80%.

7. The process as claimed in claim 6 in which said sulfuric acid has a concentration of from 60% to 70%.

8. The process as claimed in claim 1 in which the thermolysis is carried out with simultaneous distillation from the reaction medium of the a,,B-unsaturated carboxylic acid.

9. The process as claimed in claim 1, in which said total number of carbon atoms in R R and R is at least 6 and no more than 16.

10. The process as claimed in claim 1, in which said p-hydroxynitrile is selected from the group consisting of ,B-hydroxytridecanoic nitrile, fl-hydroxynonanoic nitrile, B-hydroxyundecanoic nitrile, 19 hydroxyheptadecanoic nitrile and fl-hydroxynonadecanoic nitrile, and produces said c p-unsaturated carboxylic acid correspondingly selected from the group consisting of tridecenoic acid, nonenoic acid, undecenoic acid, heptadecenoic acid and nonadecenoic acid.

11. A process for the production of long chain 11,}?- unsaturated carboxylic acids of the formula R2 Ra R1 OCOOH wherein R R and R each represent a member selected from the group consisting of hydrogen and alkyl having 3 to 22 carbons, with the proviso that the total number of carbon atoms in R R and R is at least 3 and no more than 22, consisting essentially of the steps of treating a p-hydroxynitrile of the formula R If a R1- -o-oEN (m it in which R R and R have the above assigned meanings with an aqueous mineral acid having a concentration ranging from 50% to and selected from the group consisting of hydrochloric acid, sulfuric acid, and phosphoric acid in the ratio of from 1 to 5 mols of said mineral acid, calculated as anhydrous acid, per mol of said B-hydroxynitrile at a temperature of from 80 C. to 150 C.; separating the aqueous phase; thermolyzing the resultant product at a temperature of from to 400 C.; and recovering the said oaB-unsaturated can boxylic acids.

References Cited UNITED STATES PATENTS 2,425,694 8/1947 Davis et al. 260526 N 2,790,822 4/ 1957 Wolfram et al. 260526 N 3,320,305 5/ 1967 Wiese 260526 N 3,002,023 9/ 1961 Fikentscher et al. 260526 N LEWIS GOTTS, Primary Examiner E. G. LOVE, Assistant Examiner US. Cl. X.R. 260526 N 

